The vast majority of T-cells are made in the thymus, a lymphoid organ that is particularly sensitive to radio- or chemotherapy. Strategies to enhance extrathymic T-cell development may therefore be useful to improve the outcome of conditions such as hematopoietic stem cell transplantation, cancer, immunosuppression or certain viral infections. I previously performed studies in mouse models of HSCT and malignancies demonstrating the feasibility and efficacy of adoptive cell therapy with ex vivo generated T cells (preT) to enhance T cell reconstitution. I found that adoptively transferred preT can be used as an off-the-shelf cell therapy and administered across MHC barriers to enhance thymic regeneration and T cell immunity. The main goal of this proposal is to develop strategies to enhance thymus independent T cell reconstitution in cancer patients, using tissue culture and tissue engineering based immunotherapeutic approaches. I propose to study the contribution of extrathymic sites to preT- derived T cell reconstitution, and to develop tissue constructs for T cell development ex vivo and in vivo using three-dimensional bioresorbable polymer scaffolds resembling extracellular matrix. Biodegradable polymers have the advantage that they can be used to fabricate micro or nanofibrous three-dimensional matrices for in vivo grafting, and they may be molecularly tailored to release bioactive agents resulting in highly effective localized drug delivery and control of cell growth and differentiation. T cell development will be studied in vitro and in vivo by implanting engineered stromal cell-polymer scaffold composites or cell-free thymic regeneration templates into mice followed by analysis of cell growth, differentiation, migration, and function (including anti-tumor activity). Characterization of host and biomaterial responses will also include analysis of vascularization of implants, biomaterial degradation, and inflammatory responses to implantation. Based on my preliminary data using an improved tissue engineering method with optimized design, biomaterial properties and cell-biomaterial interactions I expect that implantation of a tissue engineered artificial thymic microenvironment will result in enhanced T cell immunity and will contribute to tumor immunosurveillance. My goal over the next five years, with the help of this career development award, is to establish myself as a physician-scientist in the field of Pediatric Hematology/Oncology and to attain a tenure-track position at an academic center. As a physician-scientist, I hope to combine clinical and teaching activities with an independent laboratory-based research program with focus on clinically relevant and translational research.